Myocardial infarction, commonly known as a heart attack, is a major cause of death, disability and healthcare expense in the U.S. and other industrialized societies. For many years, doctors have thought that the main cause of a heart attack or stroke was the buildup of fatty plaque within an artery leading to the heart or brain. With time, the plaque buildup would narrow the artery so much that the artery would either close off or become clogged with a blood clot. The lack of oxygen-rich blood to the heart would then lead to a heart attack. But these types of blockages cause only a portion of the total number of heart attacks.
Researchers are now finding that many people who have heart attacks do not have arteries severely narrowed by plaque. In fact, vulnerable plaque may be buried inside the artery wall and may not always bulge out and block the blood flow through the artery. It is now believed that “soft” or vulnerable plaque is formed in the artery wall. More specifically, fat droplets are absorbed by the artery wall, which causes the release of cytokines that lead to inflammation. The cytokines make the artery wall sticky, which attracts monocytes. The monocytes squeeze into the artery wall. Once inside, the monocytes turn into macrophages and begin to soak up fat droplets. The fat-filled cells form a plaque with a thin covering made of collagen, typically type I collagen. Inflammation can predispose the thin collagen layer covering the plaque to crack, spilling the contents of the plaque into the bloodstream. The sticky cytokines on the artery wall capture blood cells (mainly platelets) that pass by the site. When these cells clump together, they can form a clot large enough to block the artery.
Current treatments for coronary artery disease include the use of stents, angioplasty, rotational atherectomy, cutting balloons, pharmaceutical agents, and lasers. However, these methods and devices are directed to treatment of hard atherosclerotic plaque and would not be effective in treating soft or vulnerable plaque. At this time no known treatment for vulnerable plaque exists. Therefore, there is a need for methods and devices to treat vulnerable plaque.